helm: Add support for remote chart version

Currently, the cilium charts are embedded inside cilium cli binary,
which will require a new cilium/charts bump in go.mod and then a new
release for cilium-cli. It's making sense to do so if some other code
changes are required to make installation working for new char version,
but most of the time, only go.mod upgrade is required.

This commit is to add the capability to install new chart version without
the need of releasing or installing new cilium-cli.

Signed-off-by: Tam Mach <[email protected]>

internal/helm/helm.go

@@ -7,7 +7,11 @@ package helm
 import (
 	"bytes"
 	"context"
+	"errors"
 	"fmt"
+	"io/fs"
+	"os"
+	"path"
 	"regexp"
 	"sort"
 	"strings"
@@ -30,6 +34,8 @@ import (
 	corev1 "k8s.io/api/core/v1"
 )
 
+const ciliumChart = "https://helm.cilium.io"
+
 var settings = cli.New()
 
 // State contains Helm state for the current Cilium installation. Cilium CLI retrieves this
@@ -186,7 +192,7 @@ func newClient(namespace, k8sVersion string) (*action.Install, error) {
 func newChartFromCiliumVersion(ciliumVersion semver2.Version) (*chart.Chart, error) {
 	helmTgz, err := helm.HelmFS.ReadFile(fmt.Sprintf("cilium-%s.tgz", ciliumVersion))
 	if err != nil {
-		return nil, fmt.Errorf("cilium version not found: %s", err)
+		return nil, fmt.Errorf("cilium version not found: %w", err)
 	}
 
 	// Check chart dependencies to make sure all are present in /charts
@@ -197,6 +203,33 @@ func newChartFromDirectory(directory string) (*chart.Chart, error) {
 	return loader.LoadDir(directory)
 }
 
+func newChartFromRemote(ciliumVersion semver2.Version) (*chart.Chart, error) {
+	pull := action.NewPullWithOpts(action.WithConfig(new(action.Configuration)))
+	pull.Settings = settings
+	pull.RepoURL = ciliumChart
+	pull.Version = ciliumVersion.String()
+
+	tempDir, err := os.MkdirTemp("", "cilium-cli")
+	if err != nil {
+		return nil, err
+	}
+	pull.DestDir = tempDir
+
+	_, err = pull.Run("cilium")
+	if err != nil {
+		return nil, err
+	}
+	file := path.Join(pull.DestDir, fmt.Sprintf("cilium-%s.tgz", ciliumVersion))
+	defer func() {
+		_ = os.Remove(file)
+	}()
+	helmTgz, err := os.ReadFile(file)
+	if err != nil {
+		return nil, err
+	}
+	return loader.LoadArchive(bytes.NewReader(helmTgz))
+}
+
 // GenManifests returns the generated manifests in a map that maps the manifest
 // name to its contents.
 func GenManifests(
@@ -218,7 +251,13 @@ func GenManifests(
 	} else {
 		helmChart, err = newChartFromCiliumVersion(ciliumVer)
 		if err != nil {
-			return nil, err
+			if !errors.Is(err, fs.ErrNotExist) {
+				return nil, err
+			}
+			helmChart, err = newChartFromRemote(ciliumVer)
+			if err != nil {
+				return nil, err
+			}
 		}
 	}
 
@@ -333,7 +372,13 @@ func ResolveHelmChartVersion(versionFlag, chartDirectoryFlag string) (semver2.Ve
 			return semver2.Version{}, err
 		}
 		if _, err = newChartFromCiliumVersion(version); err != nil {
-			return semver2.Version{}, err
+			if !errors.Is(err, fs.ErrNotExist) {
+				return semver2.Version{}, err
+			}
+			_, err = newChartFromRemote(version)
+			if err != nil {
+				return semver2.Version{}, err
+			}
 		}
 		return version, nil
 	}